In pediatric patients, the laboratory differentiation between bacterial and aseptic meningitis is unsatisfactory at the present time. What is needed are faster and more reliable tests which would allow the physician to make, quickly and unequivocally, the critical decision whether to treat immediately or withhold antibiotic therapy. Our research group at Children's Hospital National Medical Center has accumulated considerable experience with the limulus lysate test, countercurrent immunoelectrophoresis (CIE) and LDH on cerebrospinal fluids and have found them to be singularly helpful in making a rapid definitive diagnosis. Of the three, the limulus lysate test has proved to be the simplest and more reliable in our studies. The limulus test is positive even when prior antibiotic therapy has been employed before hospitalization. Hitherto, the limulus lysate assay, CIE and LDH have been performed only in the laboratory. Recently, we have been evaluating the feasibility of pre-packaging these three tests and performaing them at the bedside. The advantages of the approach are manifest in that a rapid diagnosis can be made within one hour at the bedside by the staff physician and the critical differentiation between pyogenic and aseptic meningitis can be quickly and reliably made. With 125 - 250 cases of meningitis admitted to our Infectious Disease Service annually, we will be able to assess the validity and specificity of these rapid techniques adopted to bedside use.